From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:58580 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725837AbgKBPNL (ORCPT ); Mon, 2 Nov 2020 10:13:11 -0500 Date: Mon, 2 Nov 2020 17:12:56 +0200 From: Mike Rapoport Subject: Re: [PATCH v3 2/4] PM: hibernate: make direct map manipulations more explicit Message-ID: <20201102151256.GA4879@kernel.org> References: <20201101170815.9795-1-rppt@kernel.org> <20201101170815.9795-3-rppt@kernel.org> <55cd2a4a-cfa8-d420-66b3-a25fcdd9b876@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55cd2a4a-cfa8-d420-66b3-a25fcdd9b876@redhat.com> List-ID: To: David Hildenbrand Cc: Andrew Morton , Albert Ou , Andy Lutomirski , Benjamin Herrenschmidt , Borislav Petkov , Catalin Marinas , Christian Borntraeger , Christoph Lameter , "David S. Miller" , Dave Hansen , David Rientjes , "Edgecombe, Rick P" , "H. Peter Anvin" , Heiko Carstens , Ingo Molnar , Joonsoo Kim , "Kirill A. Shutemov" , Len Brown , Michael Ellerman , Mike Rapoport , Palmer Dabbelt , Paul Mackerras , Paul Walmsley , Pavel Machek , Pekka Enberg , Peter Zijlstra , "Rafael J. Wysocki" , Thomas Gleixner , Vasily Gorbik , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org, x86@kernel.org, "Rafael J . Wysocki" On Mon, Nov 02, 2020 at 10:19:36AM +0100, David Hildenbrand wrote: > On 01.11.20 18:08, Mike Rapoport wrote: > > From: Mike Rapoport > > > > When DEBUG_PAGEALLOC or ARCH_HAS_SET_DIRECT_MAP is enabled a page may be > > not present in the direct map and has to be explicitly mapped before it > > could be copied. > > > > Introduce hibernate_map_page() that will explicitly use > > set_direct_map_{default,invalid}_noflush() for ARCH_HAS_SET_DIRECT_MAP case > > and debug_pagealloc_map_pages() for DEBUG_PAGEALLOC case. > > > > The remapping of the pages in safe_copy_page() presumes that it only > > changes protection bits in an existing PTE and so it is safe to ignore > > return value of set_direct_map_{default,invalid}_noflush(). > > > > Still, add a WARN_ON() so that future changes in set_memory APIs will not > > silently break hibernation. > > > > Signed-off-by: Mike Rapoport > > Acked-by: Rafael J. Wysocki > > --- > > include/linux/mm.h | 12 ------------ > > kernel/power/snapshot.c | 30 ++++++++++++++++++++++++++++-- > > 2 files changed, 28 insertions(+), 14 deletions(-) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 1fc0609056dc..14e397f3752c 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -2927,16 +2927,6 @@ static inline bool debug_pagealloc_enabled_static(void) > > #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP) > > extern void __kernel_map_pages(struct page *page, int numpages, int enable); > > -/* > > - * When called in DEBUG_PAGEALLOC context, the call should most likely be > > - * guarded by debug_pagealloc_enabled() or debug_pagealloc_enabled_static() > > - */ > > -static inline void > > -kernel_map_pages(struct page *page, int numpages, int enable) > > -{ > > - __kernel_map_pages(page, numpages, enable); > > -} > > - > > static inline void debug_pagealloc_map_pages(struct page *page, > > int numpages, int enable) > > { > > @@ -2948,8 +2938,6 @@ static inline void debug_pagealloc_map_pages(struct page *page, > > extern bool kernel_page_present(struct page *page); > > #endif /* CONFIG_HIBERNATION */ > > #else /* CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_DIRECT_MAP */ > > -static inline void > > -kernel_map_pages(struct page *page, int numpages, int enable) {} > > static inline void debug_pagealloc_map_pages(struct page *page, > > int numpages, int enable) {} > > #ifdef CONFIG_HIBERNATION > > diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c > > index 46b1804c1ddf..054c8cce4236 100644 > > --- a/kernel/power/snapshot.c > > +++ b/kernel/power/snapshot.c > > @@ -76,6 +76,32 @@ static inline void hibernate_restore_protect_page(void *page_address) {} > > static inline void hibernate_restore_unprotect_page(void *page_address) {} > > #endif /* CONFIG_STRICT_KERNEL_RWX && CONFIG_ARCH_HAS_SET_MEMORY */ > > +static inline void hibernate_map_page(struct page *page, int enable) > > +{ > > + if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) { > > + unsigned long addr = (unsigned long)page_address(page); > > + int ret; > > + > > + /* > > + * This should not fail because remapping a page here means > > + * that we only update protection bits in an existing PTE. > > + * It is still worth to have WARN_ON() here if something > > + * changes and this will no longer be the case. > > + */ > > + if (enable) > > + ret = set_direct_map_default_noflush(page); > > + else > > + ret = set_direct_map_invalid_noflush(page); > > + > > + if (WARN_ON(ret)) > > + return; > > People seem to prefer pr_warn() now that production kernels have panic on > warn enabled. It's weird. Weird indeed as the whole point of WARN to yell without causing a crash... I can change to pr_warn though... > > + > > + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > > + } else { > > + debug_pagealloc_map_pages(page, 1, enable); > > Reviewed-by: David Hildenbrand Thanks! > -- > Thanks, > > David / dhildenb > -- Sincerely yours, Mike.